PREVENTION 301 



■connective and fatty tissue of the dorsal mediastinum and of 

 the embedded glands should not be overlooked. With the 

 microscope the peculiar dense cell masses of the diseased con- 

 nective tissue should be looked for and the nature of necrotic 

 tissue determined in case microscopic appearances are no 

 longer reliable owing to hardening processes. 



Finallj^ it should be borne in mind that the lesions of 

 broncho-pneumonia and the interlobular changes which may 

 follow it may coexist with contagious pleuro-pneumonia, and 

 that both kinds of lesions may be encountered in the same 

 lungs. Hence, great caution must be excercised in expressing 

 an opinion when only a small portion of the lungs are pre- 

 sented for examination, because only that portion which is 

 affected with broncho-pneumonia may have been submitted. 



§ 225. Preventive inoculation and eradication. In 

 Europe inoculation has been practiced for a long time as the 

 principal means for combatting pleuro-pneumonia. As early 

 as the beginning of the last century it was proposed in Ger- 

 many by Hausmann and others. Its employment was greatly 

 increased by the investigations which were made in 1850 by 

 Willems in Holland, which were published in 1852. Since 

 that time these inoculations have been practiced in nearly 

 every country. The literature on the subject is very copious. 

 However, the value of inoculation as a protection against 

 pleuro-pneumonia has not yet received a final answer. 



The advocates of inoculation, among whom we may mention 

 Haubner, Bouley, Schiitz and others start from the well known 

 fact that one attack of pleuro-pneumonia successfully passed 

 through, confers immunity for the remainder of the animal's 

 life. By inoculation, a local, specific, inflammatory process 

 which is analogous to that in the lungs, is produced and is 

 followed by subsequent immunity of the whole body. Haubner 

 calculates that the mortality from the inoculation is from i to 

 2 per cent and that the tips of the tails are lost in from 5 to 10 

 per cent of the cases. In Holland, among 59,180 cattle 

 inoculated in 1S78 and 1879, the mortality amounted to only 

 0.66 per cent. 



The opponents of inoculation, among whom we may men- 



